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Author Topic: Thinking Northstar Conversion?  (Read 58348 times)
dguy
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Got vacuum. Want boost.


« Reply #135 on: June 04, 2004, 11:45:23 am »

The holley commander that I got from CHRFab did not come with the knock sensor wiring.

Glad you mentioned this.† It gives me something else to keep an eye out for when I start researching aftermarket PCMs more closely!
« Last Edit: June 04, 2004, 11:50:32 am by Don Guy » Logged

1984: Track car project.
1985 SE: Dead 2.8, stalled L67 swap.
aaron88
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« Reply #136 on: June 04, 2004, 12:12:07 pm »

The holley commander does have a functions for the knock sensor but it just wasnít wired up.  However; one thing I was disappointed with was that although there was a knock sensor function on the Holley Commander it doesnít have a knock counter that I can find anywhere.

Aaron

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« Reply #137 on: June 17, 2004, 11:14:33 am »

Still running speedo-less?

http://www.dakotadigital.com/Detail.cfm/-/Category=01/PartNumber=SGI-5/product.htm
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northfiero
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« Reply #138 on: June 18, 2004, 06:24:11 pm »


THANK YOU THANK YOU THANK YOU!  That was the last piece of the puzzle I was looking for!  Btw - where does the knock sensor plug in on the holley?  It's not even listed in the manual...  Do I put it on one of the "auxillary inputs" that handle A/C requests and all that?
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aaron88
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« Reply #139 on: June 21, 2004, 11:31:25 am »

Btw - where does the knock sensor plug in on the holley?† It's not even listed in the manual...† Do I put it on one of the "auxillary inputs" that handle A/C requests and all that?

I havenít had too much time to work on the wiring, but I did have time to hook up the oscilloscope.  I discovered a few interesting things.  For one there is a hell of a lot of noise coming off that block through the knock sensor.  I was recording a little over 10V at full throttle.  When I got a knock it would spike at a little over 15V.

Iíll have to do a little research to find out what kind of input the computer wants, but once I have that Iíll know if I have to make a little circuit or not.

Once you have the spark advanced (to the max minus a few) on this motor it really livens up after 4500 rpm, and I mean really livens up.  So much so that I canít even get enough fuel into the cylinders.  Iím going to have to back up the spark until I can get some bigger injectors.

More research to come.

Aaron

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aaron88
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« Reply #140 on: June 21, 2004, 11:50:42 am »

The stock size rad isn't going to be good enough for me (or should I say the way I drive sometimes, on the track of course).

Although the stock radiator will sufficiently cool the motor it doesnít respond fast enough for my liking.† While I was doing my full throttle runs to advance the spark I was noticing that the temperature was climbing a little high for my liking (around 228įF).† I was doing run after run but this is part of the fun after all. I found that it would take about 4 consecutive runs of about 1/4 mile to get the temperature up, and about 4 minutes to get the temperature down to 212 again by driving reasonably.† Iím looking for a sustainable 215 to 219įF range.

Allan from CHRFab does say that from his experience maximum power on the dino was achieved with an engine temperature around 215įF.† Aluminum motors like to run a little warmer on the coolant.

But at the same time I donít want the coolant to ever go above 225, and itís doing it now.† So to make a long story shorter Iím going to replace my radiator at some point with a 4 core radiator.

Aaron

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EDIT EDIT EDIT EDIT EDIT EDIT EDIT EDIT EDIT EDIT EDIT EDIT


I have a correction to post in regards to the size of radiator needed.

I did a whole lot more driving last night (at a track of course) and found that no matter how hard I drive the car the temp will stay under 220įF if I donít stop the car.  As long as one stays rolling, the car will not overheat.  (the stock Northstar computer doesnít turn on the rad fan until 225įF)

The reason I was having trouble before was because I would do about 4 quarter miles in a row and then pull over to adjust the tables.  The pulling over part is the reason I was having trouble with the higher heat.

So whether you need a 4 core rad or not depends entirely on what kind of driving you plan on doing.

I have now postponed my purchase of a 4 core rad until much later, maybe one or two years from now.


Aaron

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« Last Edit: June 24, 2004, 11:48:51 am by aaron88 » Logged

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« Reply #141 on: June 22, 2004, 01:04:51 am »

A closer look at how I cut my deck lid hinge.

There is more than enough strength in the bracket if itís cut properly.  First you want to make sure that there is a good radius on the cut (as indicated by arrow one).  Make sure there are no sharp edges or corners in the radius.  Secondly you want to keep the entire bend closest to the fire wall (as indicated with arrow 2).  Remember, the two brackets work together.  You can cut one or the other but not both.

Aaron

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« Last Edit: June 22, 2006, 07:02:15 pm by aaron88 » Logged

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« Reply #142 on: June 24, 2004, 12:43:29 pm »

Fiero Coolant Temp Gauge Hook-up:

I received a concerned PM on this matter and then did a little investigation.  It seems that the way I hooked up my Fiero coolant gauge sensor may not be suitable for all model years of the Northstar motor.  I found this post on PFF (by ryan.hess about ĺ of the way down)
http://www.fiero.nl/forum/Forum2/HTML/043632-2.html
It seems to indicate that for 93 to 95 Northstars the plug I used on the coolant crossover manifold opens to the EGR gas and not the coolant.  The 96 to 99 models are open to coolant on the other side of the plug.  Iím not sure if this means that 2000 + models donít even have the plug, but I will find out what is going on with this coolant manifold and post an update.

Alternately ryan.hess gives a viable solution to an alternate location for the sensor, however; this is the ideal location to bleed out all the remaining air from the block when filling the coolant system.  Therefore I would have to recommend against this location for that reason only (it can be really hard to get the air out of the system without this throttle body coolant line).

Aaron

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northfiero
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« Reply #143 on: June 24, 2004, 11:50:41 pm »

So much so that I canít even get enough fuel into the cylinders.† Iím going to have to back up the spark until I can get some bigger injectors.

Wait a sec...  You're running a stock 98 engine right?  How could it be going lean?   Shocked
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aaron88
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« Reply #144 on: June 30, 2004, 11:31:45 am »

(Sorry, but my internet has been down for a few days)

To answer the previous question, Iím advancing the spark.  So because Iím igniting the fuel earlier and itís at a higher mean pressure, the fuel has more time to burn and will also burn faster, therefore burn more fuel in the same given time (one stroke).

Basically advancing the spark does some things that can be considered beneficial for peak performance.† Because the motor has already been designed to resist knock by having modest spark tables (due to the fact that the manufacture knows that the owner of said motor may decide to use regular gas).† Therefore advancing the spark while using 91 to 92 octane fuel can allow one to make better use of the fuel going into the cylinder to burn, but only if the geometry of the stroke will accommodate it.† Some of the advantageous things are; starting the burn earlier so that more fuel can be burned and getting the energy of the expanding gas in the most favourable position of stroke.

There are a number of things that determine the amount of power you can get out of one stroke.† Spark advance simply determines the timing of the process.† Other things to consider are the temperature of the piston head and cylinder walls, the resistance of the fuel to igniting under pressure (indicated by the octane rating), the amount of fuel in the cylinder, the amount of oxygen in the cylinder, the flame propagation rate of said fuel under the pressure of compression before ignition (aprox 147 psi for the Northstar) and the changing rate thereafter as the pressure increases and then decreases (due to burn and stroke).† The size of the bore, the length of the stroke, the average angle the piston rod acts on the crank at the point of mean exertion due to ignition, and the strength of all components involved (to determine the feasibility of any power increase and itís safety factor).

Now before I go on I think I should mention that I donít know much about auto mechanics nor do I know much about the combustion process, but what I do know and understand is physics.

Instead of going through the whole calculation manually (which would only give me a starting point anyway) Iím going to make some assumptions and move on form there.

Assuming that the motor has been designed properly, Iím going to negate most of everything aforementioned in my experiment in order to make it as understandable as possible.† Advancing the spark may not yield more power and the reason for this has to do with the factors mentioned above.† But the thing to remember is that most motors have been designed with a certain octane in mind.† Also most motors these days will produce maximum power somewhere between maximum advance before knock and a few degrees after that, at an O2 voltage of about .84v.† So what one must do; is make up several spark and corresponding fuel tables (varying advance along the table) and run them all on a Dino, then mix and match according to the results and re-test.† Until I do this I wonít know what the most advantageous advance is.

But one thing I do know is that I canít even do this experiment with the fuel injectors I have now, because they simply will not spray enough fuel.† The farther I advance the spark more fuel I need to add and as it stands now I canít even approach the maximum advance and get near enough fuel in the cylinder.† My duty cycle is approaching 90% and Iím only at 32į total advance.† My knock sensor testing showed that I should be able to advance a few degrees more all across the table before knocking.

Also something else to take into consideration is the fact that I may be adding more aggressive cams and stiffer valve springs.† If I do this I will definitely need much larger injectors simply due to the fact that I will have less time to inject fuel (due to a higher rpm), the duty cycle on the injectors is already too high.† Iím trying to keep it below 80%.


Aaron

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northfiero
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« Reply #145 on: June 30, 2004, 05:15:38 pm »

Wow, I just learned something  Shocked  So when you get it completely tuned, you gonna post the fuel/spark tables here?  Grin
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aaron88
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« Reply #146 on: July 01, 2004, 12:50:34 pm »

I will post the fuel and spark tables when Iím done.
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aaron88
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« Reply #147 on: September 01, 2004, 02:35:12 am »

Well I finally got around to calling Holley and asking them for the knock control information.  I was told that in order to make things easy there was a Holley sub-harness I could buy that would plug into the existing one (Holley part number 534-136), interfacing with (Holley Commander 950) pin B7 (knock control).  Basically all you need is a stock GM knock module to plug into the knock sensor on one end and pin B7 on the other (you donít really need their harness but it might make things easier).  The only problem is that the Northstar isnít an iron block.  And Iím not sure about this but Iím pretty sure about this, that with an aluminum block you canít use an iron block knock module.  The vibration transferred through the two blocks are very different.  All of the GM aluminum block knock modules that I know of are multi pin units located inside the ECM.  This complicates things.

If someone could confirm what knock module would work for this application it may save me some time. Undecided

Iím still a little busy to do this right away, but I should be able to get to this sometime in the next month.  Iíll either have instructions for using the stock Northstar module or have an alternate circuit to use.

The knock sensor wire is the little blue one running right next to the purple starter wire.  They both go under the intake on the front of the motor (right side).


Aaron

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« Last Edit: June 22, 2006, 07:03:29 pm by aaron88 » Logged

Your only limitations are set from within, by a lack of vision.  But to have vision alone leaves the process idle.  Ergo, without action your thoughts are worthless.
northfiero
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« Reply #148 on: September 24, 2004, 10:50:27 am »

Couple things to post:

first off, the knock sensor is (as mentioned) located under the intake manifold for 96-99 (not sure about y2k+) models.  However, 93-95 the knock sensor is on the rear side of the engine, closest to the crank pulley. 

secondly, you were mentioning that when a knock occured, there was a 15V spike according to your scope.  I don't remember/know which pins on the holley have which functions, but I believe you can have a knock sensor input either be +12 or gnd.  It seems to me like it would be a fairly simple circuit to convert a 15V pulse into a 12V square pulse or ground pulse whichever the case may be.  Couple diodes/resisters and a transistor if a ground pulse is needed. 
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stroker
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« Reply #149 on: October 03, 2004, 10:10:05 pm »

hi all
i'm new to the forum and got in cause i liked the way you guy's run around the north*
i have one running fiero and one for parts and getting my 60 000 miles 4.6 this week off a 99 sls plus tranny and computer
only gonna go in the car when i pull car off the road next winter so it gives me a year to plan and developpe things for this beast

glad from central qc,only 3.5 hrs drive from ottawa

marc the stroker.
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